Green Propellant

The U.S. Air Force has developed an advanced, high-density, monopropellant formulation family entitled “Monopropellants of Lessened Toxicity (AF M315E)” (henceforth, Green Propellant). The patent application, U.S. Patent 09/322,786 (under secrecy order), is not issued, but is “allowed.” This technology is ITAR (International Traffic in Arms Regulations)-restricted. By a nonexclusive license agreement, Green Propellant has been transferred to Digital Solid State Propulsion (DSSP), a small U.S. company located in Reno, Nevada. Under this agreement, DSSP is the go-to commercial source of Green Propellant, and is licensed to sell it to other U.S. federal agencies and commercial companies for spacecraft propulsion.

Green Propellant represents a high-performance, low-toxicity alternative to the state-of-the-art spacecraft propellant, hydrazine. It is primarily comprised of energetic ionic liquids (EILs), which confer high energy-density in addition to having negligible vapor pressures. The propellant offers a 50-percent improvement in volumetric impulse, which translates to either significantly increased spacecraft lifetimes or performance for a given tank size, or smaller spacecraft. The negligible vapor toxicity results in improved safety as well as lower operational and handling costs with faster turnaround times. Hydrazine has been used in the U.S. space program since the 1970s as the low-power monopropellant for maneuvering the thrusters of spacecraft; however, it has serious disadvantages. It is highly toxic when inhaled, corrosive on contact with skin, and hazardously flammable. It can cause seizures and coma; and acute exposure can damage the liver, kidneys, and central nervous system. Consequently, when handling hydrazine, people must wear self-contained atmospheric protective ensemble (SCAPE) suits and breathe supplied air.

Green Propellant provides a nontoxic alternative to hydrazine, and can be handled with standard personal protective equipment. Adam Brand, Principal Engineer, Air Force Research Laboratory, Aerospace Systems Directorate, Rocket Propulsion Division (AFRL/RQR) is the inventor of Green Propellant. Brand began working on Green Propellant in 1997 with a team of four researchers who provided background and technical information. To transfer Green Propellant to industry, he undertook an extensive search for relevant U.S. companies. Brand identified DSSP, the perfect partner to whom AFRL/RQR would license the technology and who would manufacture and market the groundbreaking propellant. Kristen Schario is the AFRL/RQR Technology Transfer Manager who negotiated the nonexclusive license agreement and addressed myriad issues related to the secrecy order on the patent. She worked with the Air Force legal team to ensure that Green Propellant could be licensed and that the secrecy order was not being violated in the process. Successful transfer of the technology to DSSP ensures a stable commercial source of this nontoxic, high-performance spacecraft propellant to the U.S. community in support of Air Force and DoD missions and the U.S. spacecraft industry.